1. Technical Field
The present invention relates to an image display apparatus in which an illumination system illuminates a liquid crystal panel or any other similar component to form an image thereon, and a projector.
2. Related Art
In an image display apparatus, a dichroic mirror and other optical elements have a dependence on the angle of incidence of a light beam, and optical characteristics such optical elements (specifically, a cutoff half-height wavelength, for example) change with the angle of incidence of a light beam. Therefore, for example, optical characteristics of an inclined dichroic mirror disposed in a color separation system change in the plane of the dichroic mirror, disadvantageously resulting in variation in color characteristics of the image display apparatus. To address the problem, there is an apparatus capable of eliminating a dependence on the angle of an incident light beam by employing gradient characteristics in the right-left direction (corresponding to the longitudinal right-left direction of the plane) of a multilayer film of a dichroic mirror to change the dichroic characteristics in accordance with the angle of incidence (see JP-A-3-291644, for example). There is another apparatus capable of preventing deviation in optical characteristics by providing unevenness in thickness or in refractive index that is gradient in a specific direction of a dichroic mirror (see JP-A-6-18834, for example).
The dichroic mirrors described above, in which gradient optical characteristics are simply introduced, for example, in the right-left direction, however, cannot exactly or approximately eliminate the dependence on the angle of a light beam. The dependence on the angle of an incident light beam is therefore still present, disadvantageously resulting in residual unevenness in color of a projected image.